linux-kernel - [PATCH 1/2] workqueue: remove unneeded test before wake up next worker

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Message-ID: <1405505409-12058-1-git-send-email-laijs@cn.fujitsu.com>
Date:	Wed, 16 Jul 2014 18:09:58 +0800
From:	Lai Jiangshan <laijs@...fujitsu.com>
To:	<linux-kernel@...r.kernel.org>
CC:	Tejun Heo <tj@...nel.org>, Lai Jiangshan <laijs@...fujitsu.com>
Subject: [PATCH 1/2] workqueue: remove unneeded test before wake up next worker

In this code:
	if ((worker->flags & WORKER_UNBOUND) && need_more_worker(pool))
		wake_up_worker(pool);

the first test is unneeded. Even the first test is removed, it doesn't affect
the wake-up logic when WORKER_UNBOUND. And it will not introduce any useless
wake-up when !WORKER_UNBOUND since the nr_running >= 1 except only one case.
It will introduce useless/redundant wake-up when cpu_intensive, but this
case is rare and next patch will also remove this redundant wake-up.

Signed-off-by: Lai Jiangshan <laijs@...fujitsu.com>
---
 kernel/workqueue.c |    7 ++-----
 1 files changed, 2 insertions(+), 5 deletions(-)

diff --git a/kernel/workqueue.c b/kernel/workqueue.c
index f8d54c1..6d11b9a 100644
--- a/kernel/workqueue.c
+++ b/kernel/workqueue.c
@@ -2047,11 +2047,8 @@ __acquires(&pool->lock)
 	if (unlikely(cpu_intensive))
 		worker_set_flags(worker, WORKER_CPU_INTENSIVE, true);
 
-	/*
-	 * Unbound pool isn't concurrency managed and work items should be
-	 * executed ASAP.  Wake up another worker if necessary.
-	 */
-	if ((worker->flags & WORKER_UNBOUND) && need_more_worker(pool))
+	/* Wake up another worker if necessary. */
+	if (need_more_worker(pool))
 		wake_up_worker(pool);
 
 	/*
-- 
1.7.4.4

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